The present invention relates to an electronic leveling apparatus and associated leveling staff capable of measuring the height difference and distance between the positions automatically through the opto-electric conversion of the image of a pattern formed on the leveling staff, and particularly to an electronic leveling apparatus and associated leveling staff, with the apparatus having a drive means for turning it on a horizontal plane to detect the staff and being operative to focus the pattern image of the staff automatically.
For the direct measurement of the ground level or the like, a set of leveling unit and leveling staff has been used conventionally. The leveler uses the leveling unit to view the scale on the leveling staff and measures the difference of height between the two positions. However, this traditional leveling scheme involves a read error made by the leveler. With the intention of overcoming the leveler's read error, electronic leveling systems in which the scale on the leveling staff is read electronically have been developed. One electronic leveling system is designed to emit a prescribed optical signal from the leveling staff and receive and identify the optical signal on the leveling unit thereby to read the scale on the leveling staff.
The applicant of the present invention has developed an electronic leveling apparatus that is operative to determine the height difference between positions electronically, as described in U.S. patent application Ser. No. 08/082,082 now abandoned. This electronic leveling apparatus uses a leveling staff 2 having a cyclic arrangement of a pattern set, with each block consisting of a first pattern A, second pattern B and third pattern R at a constant pitch of p, as shown in FIG. 2.
The lowest pattern block is defined to be block 0 which includes R(0), A(0) and B(0), the next block is block 1 including R(1), A(1), B(1), the next block is block 2 including R(2), A(2), B(2), and so on. A reference signal is produced in correspondence to the constant pattern pitch p. The third pattern R has a constant length of 8 mm for its black section, whereas the first pattern A has its length modulated to have a period of 600 mm and the second pattern B has its length modulated to have a period of 570 mm.
However, the above-mentioned electronic leveling apparatus for evaluating the height difference automatically requires the accurate visual sighting of the leveling staff by the leveler. This tedious sighting operation must be repeated each time the leveling staff is moved, which retards the improvement of the efficiency of leveling work.